The invention is directed to synthetic silicatic fillers modified with organosilicon compounds, a process for their production and their use in vulcanizable rubber mixtures.
It is known to treat oxidic surfaces with organosilicon compounds in order to improve the bond between oxidic filler and organic polymers of the most varied chemical composition and therewith to improve the reinforcing properties of the filler in the polymer by this treatment.
For example, for this purpose the organosilicon compound in question can be dissolved in an organic solvent and this solution used subsequently to treat, e.g., clay (Papalos, U.S. Pat. No. 3,227,675).
It is known from Iannicelli U.S. Pat. No. 3,567,680 to modify silica suspended in water with mercapto and aminosilanes. However, the organsilicon compounds in question in the amounts needed for the modification are water insoluble so that in this case also the treatment of the filler is carried out from a solution.
The task of the present invention was to find rubber compatible synthetic silicatic finely divided fillers modified with water insoluble organosilicon compounds and a process for their production in which the operation can be carried out solvent free (i.e., organic solvent free) in aqueous phase in spite of the water insolubility.